Alkoxylated derivatives of fluorinated alcohols having a low alkoxylation degree, typically ranging from 2 to 10, and in particular ethoxylated derivatives of (per)fluoropolyether (PFPE) alcohols, are useful building blocks for the synthesis of further functional derivatives and mixed copolymers. Indeed, the presence of a short polyethyleneoxy chain at the polymer ends improves compatibility with hydrogenated reagents, which is particularly desirable in the synthesis of copolymers with hydrogenated blocks. Compatibility with hydrogenated compounds may also be an advantage in the manufacture of compositions wherein a PFPE alcohols is to be mixed with hydrogenated ingredients.
However, while ethoxylated derivatives of PFPEs alcohols having an ethoxylation degree from 1 to about 2 can be synthesised by reaction of a PFPE alcohol with ethylene oxide in the presence of a catalytic amount of the corresponding PFPE alkoxide, ethoxylated derivatives having an ethoxylation degree equal to or higher than 2 cannot.
In order to overcome this drawback, attempts to develop alternative methods have been made.
A number of prior art documents disclose the use of boron-based catalysts in the manufacture of ethoxylated derivatives of fluorinated alcohols.
For example, inventor's certificate SU 570590, granted to Fedorov V. A. et al. on Aug. 30, 1977, relates to the synthesis of non-ionic surface agents by reaction of fluorinated alcohols of formula H(CF2)nCH2OH, in which n ranges from 4 to 12, with an alkylene oxide in the presence of boron trifluoride etherate as catalyst.
U.S. Pat. No. 4,490,561 (CONOCO INC [US]) 25 Dec. 1984 discloses a method for the alkoxylation of fluorinated alcohols which comprises contacting a fluorinated alcohol with an alkoxylating agent in the presence of a catalyst selected from a specific group (reference is made in particular to claim 1). The group includes, inter alia, a BF3/M(R)q catalyst, wherein M is a metal selected from gallium, indium, thallium, zirconium, hafnium, aluminium and titanium, q is equal to the valence of M and R is hydrogen, fluorine, an alkyl group, or an alkoxy group. In particular, fluorinated alcohols that can be submitted to this ethoxylation methods comply with the following formulae (reference is made in particular to col. 2, lines 41-63):Rf(CH2)aOH  (5)RfSO2NR2−R1−OH  (6)RfCH═CH(CH2)aOH  (7)RfCONR2−R1−OH  (8)wherein Rf represents straight or branched perfluoroalkyl groups, R1 is an alkylene group containing from 2 to 30 carbon atoms and R2 is, independently, hydrogen, halogen, or an alkyl group containing from 1 to 30 carbon atoms.
WO 95/35272 A (DU PONT [US]) 28 Dec. 1995 discloses a process for the preparation of mixtures of fluoroalkoxylates of formula:F(CF2)m—(CH2)n—(OCH2CH2)p—OHwherein:
F(CF2)m is a linear perfluoroalkyl group;
m is an integer in the range between 2 and about 20;
n is an integer in the range between 1 and 3; and
p is an integer in the range between 1 and about 40;
said process comprising reacting a perfluoroalkanol of formula:F(CF2)m—(CH2)n—OH
wherein m and n are as defined above
with ethylene oxide in the presence of a catalyst consisting essentially of a mixture of an alkali metal borohydride and at least one source of iodine selected from elemental iodine, alkali metal iodides, and alkaline earth metal iodides.
WO 96/28407 (DU PONT [US]) 19 Sep. 1996 (corresponding to U.S. Pat. No. 5,608,116), relates to a process for preparing fluoroalkyl ethoxylated alcohols by reaction of a fluorinated alcohol with an alkylene epoxide having from 2 to 10 carbon atoms, in particular, ethylene oxide, in the presence of an alkali metal borohydride and of at least an iodine source. In particular, the fluorinated alcohol complies with formula:Rf-Q-OHin which Rf is a linear or branched perfluoroalkyl group having from 4 to 20 carbon atoms, or a mixture of these groups; andQ is —(CH2)n—, —SO2NR1R2— or —C(O)—NR3R4—wherein each of R1 and R4 is independently hydrogen or an alkyl group containing from 1-6 carbon atoms; each of R2 and R3 is independently a divalent linear or branched alkylene group containing from 1-6 carbon atoms; and n is an integer of from 1 to 6.
U.S. Pat. No. 8,039,677 B (DU PONT [US]) 4 Nov. 2010 relates to fluoroalkoxylates to be used for altering the surface behaviour of liquids. In particular, this document discloses fluorinated alkylalkoxylates containing a perfluoroalkyl group having less than 8 carbon atoms, which are prepared by means of a process comprising reacting an alcohol of formula:Rf—(CH2CF2)n(CH2)m—XH  (4)in which:
Rf is a linear or branched perfluoroalkyl group of 1 to 6 carbon atoms;
n is an integer from 1 to 4;
X is O; and
m is an integer from 1 to 6,
with one or more alkoxylating agents, such as alkylene epoxide, in the presence of a catalytic system comprising (1) at least one alkali metal borohydride and (2) at least one quaternary salt. Optionally, an iodine source can be present in the catalytic system. The results reported in the examples (reference is made in particular to tables 1 and 3) disclose in particular fluoroalkoxylates with an alkoxylation degree between 6 and 7.
WO 2010/127221 A (DU PONT [US]) 4 Nov. 2010 specifically discloses and claims a process as defined in U.S. Pat. No. 8,039,677 wherein the alkoxylating agent is an alkylene oxide having from 2 to 10 carbon atoms.
WO 2009/073641 (CHEMGUARD LTD) 6 Nov. 2009 relates to a method of forming an alkoxylated fluoroalcohol comprising combining:                a boron compound having or providing at least one boron-oxygen bond and an iodine source with        a fluoroalcohol and an alkylene oxide        in the presence of a base and        
allowing the reactants to react to form an alkoxylated fluoroalcohol reaction product.
As fluoroalcohol subjected to the ethoxylation method, this document specifically mentions only a monofunctional perfluorinated alkyl alcohol of formula:F(CF2)m—OH or F(CF2)m-A—OHin which:
m usually ranges from 2 to 20, more preferably from 4 to 14, and
A can be a group of formula —(CH2)n—, —SO2NR1R2 or a group of formula —C(O)NR3R4—, wherein n is from 1 to 6, R1 and R4 are each independently selected from hydrogen, halogen and a C1-C30 alkyl group and R2 and R3 are each independently selected from a C2-C30 alkylene group.
Boric acid or alkyl borates, potassium iodide, ethylene oxide and KOH are specifically mentioned respectively as boron compound, iodine source, alkylene oxide and base.
Alkoxylation of mono- and bi-functional PFPE alcohols is not mentioned or suggested in this document. Furthermore, this document teaches (reference is made to the paragraph bridging pages 9 and 10 and to examples 1 to 3) to carry out the alkoxylation reaction by first adding a base, namely NaOH, to the fluoroalcohol, followed by addition of the iodide source and of the boron compound; finally, the alkoxylating agent is added and the mixture is heated up to a temperature which might reach 200° C. in order to allow the ethoxylation reaction to proceed. In particular, it stems from examples 1 to 3 that the stoichiometric ratio between the base and boric acid or alkyl borate is lower than 1:1 and that the temperature raises at most to 155° C. However, attempts made by the applicant to carry out the ethoxylation of PFPE alcohols (in particular PFPE alcohols having —CF2—CH2OH end groups), following this teaching did not provide the expected results, as shown in the following Experimental section in comparative example 4.
WO 2010/127230 A (DU PONT) 11 Nov. 2010 discloses a process for preparing alkoxylated alcohols alkoxylate of the formula R1O(QO)mH wherein m is from 1 to 20, said process comprising contacting one or more alcohols of the formula R1OH with one or more 1,2-alkylene epoxides of the formula Q(O), wherein:                Q is a linear alkylene group of the formula CyH2y+1 where y is an integer of from 2 to 10, and        R1 is a linear, branched, cyclic, or aromatic hydrocarbyl group, optionally substituted, having from 1 to 30 carbon atoms.        
The process, aimed at avoiding the use of strong bases, envisages the use of a catalyst at a molar ratio of alcohol to catalyst of from about 200 to 15, wherein the catalyst is MB(OR1)x(X)4-x or B(OR1)3/MX, and wherein M is Na+, K+, Li+, or R2R3R4R5N+, R2R3R4R5P+, and R2, R3, R4, and R5 independently are hydrocarbyl groups, X is Br, F or I and x is 1 to 3. The process is carried out at a temperature from about 60° C. to about 200° C. and at a pressure from ambient atmospheric pressure to about 1,035 KPa.
This document teaches that the process includes contacting the fluorinated alcohol with an alkylene oxide in the presence of the catalyst and it states that “the alcohol and catalyst can be added to the alkylene oxide either simultaneously or in any order” and that “the catalyst is either added to or generated in, the neat alcohol, which also serves as solvent for the reaction” (reference is made to page 5, lines 28-32).
This prior art document does not specifically disclose or suggests the alkoxylation of mono- or bifunctional PFPE alcohols. Attempts made by the applicant to carry out the ethoxylation of such alcohols (in particular PFPE alcohols having —CF2—CH2OH end groups) following the teaching therein contained, in particular at examples 34 and 35, wherein no alkoxide of the fluorinated alcohol is used, in order to obtain ethoxylated derivatives with an ethoxylation degree of at least 2 did not provide the expected results, as shown in the following Experimental section in comparative example 5.
WO 2012/139070 (E.I. DU PONT DE NEMOURS AND COMPANY) is directed to fluoroalkoxylates having formula:Rf—O—(CF2)x(CH2)y—O-(QO)z—H  (1)
Rf is a linear or branched perfluoroalkyl having 1 to 6 carbon atoms optionally interrupted by one to three ether oxygen atoms;
x is an integer of 1 to 6;
y is an integer of 1 to 6;
Q is a linear 1,2-alkylene group of the formula CmH2m where m is an integer of 2 to 10; and
z is an integer of 1 to 30.
This document teaches to prepare the compounds of formula (1) in the presence of a catalyst system comprising (a) at least one boron-containing compound and (b) a source of iodine or bromine. In greater detail, in Examples 1 it is taught to prepare a mixture of perfluoropropylvinylether alcohol (PPVE alcohol), a boron-containing compound (sodium borohydride) and an iodine compound (sodium iodide); the mixture is then treated with ethylene oxide to obtain ethoxylates with varying linkages. In Example 2 it is taught to charge a reactor with HOCH2CH2CF2CF2OCF2CF2CF3, 6% mol of the corresponding triboric ester and 6% mol tetrabutylammonium iodide and then treating with ethylene oxide to obtain a compound with an ethoxylation degree of 8. No specific mention is made of the alkoxylation of fluorinated alcohols ending with a —CF2—CH2OH moiety and of the use of an alkoxide of the fluorinated alcohol in the process.
The need was thus felt to provide a convenient industrial process for the manufacture of alkoxy derivatives of PFPE alcohols having an alkoxylation degree of at least 2.